Policy services are used to deny or allow access to content or other data on a computer network. Policy services are also used to filter such content. It is common for policy services to be used to prevent users of client computers, such as children, from accessing material that is unsuitable for them.
However, access to content or other data can be initiated in a number of ways. When a domain name or other hostname is used, policy services can enforce stored policies based on the domain name or hostname. When a network address, such as an Internet protocol (IP) address, is used to access such content, it can be more difficult to consistently enforce policy, since the mapping of network addresses to hostnames may change over time. In fact, some hostnames change network addresses quite frequently, such as several times a day.
If the mapping of network addresses to hostnames is inaccurate, then there are times when policy is inadvertently enforced on benign content or not enforced on content intended to be blocked or filtered.